In vitro and in vivo reconstruction of cutaneous stem cell system

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We studied the outgrowth pattern of keratinocytes forming mono-layer sheet. We hypothesized that keratinocytes should balance the tension one another and we could prove it. After keratinocytes stratified, they stopped migrating and proliferating even if there was enough room for them. We demonstrated that keratinocytes produced unknown inhibitory molecules and secreted them in the culture medium. We performed mRNA analysis by differential display methods, but we have not identified the molecule yet.We focused on the dermal papilla cells because they are key players of hair follicle development. Recently, multipotent stem cells have been isolated from the skin and designated as skin-derived precursors (SKPs) that are localized in the dermal papilla of hair follicles. We found that CD133, a putative stem cell marker for hematopoietic cell, was expressed in the dermal papilla cells and was a novel cell surface marker for the DP cell. We could isolate the DP cells from embryonic and adult mice skin by using this marker and proved that CD133 positive cells had hair follicle-inducing ability. Moreover CD133 positive cells differentiated neuronal and mesodermal lineage cells. We also succeeded in culturing DP cells for a long time with keeping hair follicle-inducing ability. Furthermore we demonstrated that artificially aggregated DP cells promoted hair follicle induction when they were combined with epidermal cells in vivo. We noticed that when the hair follicle was reconstructed, sebaceous glands were accompanied at the same time. We also confirmed that cultured dermal papilla cells became dermal sheath cells as well as dermal papilla cells in vivo. Our observations imply that dermal papilla cells may rebuild their microenvironment and behave as both dermal papilla cells and dermal sheath cells as they adjust.